Such steering kites, which can for example be styled as so-called tube kites or soft kites, are generally known. The tube kites get their aerodynamic form by inflation of form-giving elements. Soft kites get the intended aerodynamic shape by picking up air during the first flight minutes. Normally, the steering kites are controlled and steered into the intended direction by two or four flight lines and a corresponding steering device to which the flight lines are attached. Frequently, the arrangement is made such that the steering kite is attached in a relatively firm way to the body by two force lines of the four flight lines via a tie-bar. The steering kite is steered by the two other flight lines, the steering lines. An additional third or fifth line is used as security line or as start line. Such a steering kite can catch very strong wind forces, and it is known to use these for the propulsion of a vehicle, for example a beach buggy or a surfboard.
The propulsion of a boat by means of wind force takes place in the classical manner by a sail that is attached to a vertically aligned mast. Optimal wind exploitation should be caused by a multiplicity of sails. However according to the alignment of the sail at the mast, the boat is inclined by the wild to the wind-averted side. A force-component is generated downwards as a consequence of this inclination whereby the boat is pressed more deeply into the water and therefore the displacement resistance will be increased. Moreover, the effective wind capturing area of the sail decreases in the driving direction. Thus, speed keeps within limits.
From U.S. Pat. No. 4,497,272 and DE 35 18 131 A1 it is known to drive boats with the help of so called floating sails. Here, the sails are only attached over support cables to the boat and are held up with a balloon. Generally, a force component of the wind force can also be generated with such floating-sails in such a way, that the wind-averted side of the boat immerses more deeply into the water. This has a consequence that a capsize of the boat is inevitable with too strong wind forces, since a floating-sail always offers the same wind-capturing area despite the increasing inclination of the boat in contrast to conventional sails.
From document DE 1 99 28 166 A1 a boat is known which is driven by a steering kite, in which the point of application of force of the force line or force lines should lie at the same height or below the form centre of gravity or centre of buoyancy. For this, a guiding rail is provided which moves the linking point of the force lines over the hull downward in direction of the keel. Therefore, the kite is positioned on the one or the other side of the boat and at least one force line of the kite runs below the waterline. It is obvious that such a construction of an attaching-device for the steering kite entails considerable problems.
Document EP 0 853 576 B1 discloses a boat, to which a kite-sail is attached by a rotating arm. In particular, the configuration here is chosen in such a way that the rotating arm is linked to the boat essentially at a position in which the conventional vertical mast would be positioned. Means are provided to swing the rotating arm around a horizontal axis, so that the outer end with the flight lines holds a relative position to the boat in which the wind-averted side of the boat is lifted from the water. The use of such a rotating arm has the disadvantage that it needs sufficient movement-area on the boat-deck due to its turning stiff construction. Also, the rotatable and pivotable bearing of the rotating arm at the linking point is extremely complicated and exposed to very high forces. Furthermore, the equipment for the rising or lowering of the rotating arm needs an extended space.